Pleistocene Gobiid Fishes of the Genus Rhinogobius

Bull. Kitakyushu Mus. Nat. Hist., 7: 111-119. December 20, 1987
Pleistocene Gobiid Fishes of the Genus Rhinogobius
from Kusu Basin, Oita Prefecture, Japan
Yoshitaka Yabumoto
Kitakyushu Museum of Natural History, Nishihonmachi,
Kitakyushu, 805 Japan
(Received August 21, 1987)
Abstract Two species of Pleistocene gobiid fishes, Rhinogobius giurinus and R. brumous,
were collected from the diatomite bed at Kusu Basin in Oita Prefecture, Japan. These
species are identified by characters of the pelvic fin and scales. From Kusu Basin, a
salmonid species, Oncorhyncus cf. 0. masou or 0. rhodums, and three cyprinid species
Hemibarbus barbus, Zacco temminckii, and Acheilognathus lanceolata were reported by Uyeno et
al. (1975). This is the first record of gobiid fishes which were found from this deposit.
A number of fossil specimens belonging to the family Gobiidae were collected from
Nogami Member in Kusu Formation at Nogami in Kusu Basin, Oita Prefecture. This
Formation and Member were first described by Shuto (1953) who made a geological
survey of the upper area of Kusu River, and named it as Kusu Formation and recognized
three Members: Hosenji, Nogami, and Hijiu Member in order from bottom to top. The
age of Nogami Member is Middle Pleistocene (Iwauchi and Hase, 1987). Uyeno, et al.
(1975) reported freshwater fish fossils from Nogami Member. These are a salmonid
species, Oncorhyncus cf. 0. masou or 0. rhodums, and three cyprinid species, Hemibarbus
barbus, Zacco temminckii, and Acheilognathus lanceolata.
Two species of gobiid fossil fishes of
the genus Rhinogobius are reported here for the first time from Kusu Basin.
Acknowledgments
I am very grateful to Dr. Teruya Uyeno of the National Science Museum for his
invaluable advice and critical reading of the manuscript. I would like to express my
sincere gratitude to Mr. Akinori Takayama of the Hakusan Kogyo Corporation for the
donation of his specimens and his cooperation in collecting other specimens. I thank Mr.
Tsugito Nagashima for the first information of the yielding of the specimens. I am
grateful to Dr. Nobuaki Mizuno of Ehime University for the donation of some forms of
Recent specimens of R. brunneus, and to Mr. Muneyoshi Hayashi of the Yokosuka City
Museum for information on the distribution of Recent species of the genus Rhinogobius. I
am also grateful to Dr. Ryuzo Toriyama and Dr. Masamichi Ota of the Kitakyushu
Museum of Natural History for their constant encouragement.

112 Yoshitaka Yabumoto
Material:
Class Osteichthyes
Order Perciformes
Family Gobiidae
Rhinogobius giurinus (Rutter)
Specimens were collected by Akinori Takayama, Teruya Uyeno, and
Yoshitaka Yabumoto between 1983-1986.
KMNH (Kitakyushu Museum of Natural History) VP 100,117, almost complete
specimen with dorsal side exposed, but first dorsal fin and anal fin missing. Head region
well preserved. Standard length 19.8 mm and number of vertebrae 10+16=26. This
specimen is identified by the form of the pelvic fin. KMNH VP 100,118, almost complete
specimen with its left side exposed, but second dorsal fin missing. Scales of the posterior
part of the body are well preserved. Standard length 24.8 mm and number of vertebrae
10+16=26. This specimen is identified by the form of the scales. KMNH VP 100,119,
almost complete specimen with ventral side exposed, but first dorsal fin, a part of 2nd
dorsal fin and pelvic fin missing. Standard length 20.6 mm and number of vertebrae 10
+ 16=26. This specimen is identified by the form of the scales. KMNH VP 100,120,
almost complete specimen with its right side exposed, but lacking dorsal fin, a part of anal
fin and some bones of head region. Standard length 26.1 mm and number of vertebrae
10+16=26. This specimen is identified by the form of the pelvic fin. KMNH VP
100,121, almost complete specimen with its right side exposed, but lacking pectoral fin,
pelvic fin, anal fin and a part of head region. Scales are preserved on abdominal part
and are detached from caudal part. Standard length 25.6 mm. This specimen is
identified by the form of the scales. KMNH VP 100,122, almost complete specimen with
its right side exposed. Scales are preserved. Standard length 26.0 mm and number of
vertebrae 10+16=26. This specimen is identified by the form of the scales. KMNH
VP 100,123, anterior part of the body and caudal fin with its left side exposed, scales
preserved on the part below second dorsal fin. Standard length 24.1 mm. This
specimen is identified by the form of the scales. Takayama's specimen 1, almost
complete specimen with its left side exposed, but lacking a part of head region and anal
fin. Scales are preserved. Standard length 27.0 mm and number of vertebrae 10+16=
26. This specimen is identified by the form of the scales. KMNH VP 100,124, some
bones ofhead region, pectoral fin, dorsalspines, and scales are preserved. This specimen
is identified by the form of the scales.
Distinguishing characters: The branching point of the innermost pelvic fin ray is
approximately in between the base and the branching point of the next ray. The
posterior end of each scale is slightly pointed. The spines of each scale are short at the
posterior corner and gradually become longer toward the dorsal and ventral ends of the
posterior margin. Grooves extend close to the posterior margin of the scales.
Description: Scales are ctenoid. The frontal bone is wide at the posterior part
and rapidlynarrows at theanteriorpart. The sensory canalis presenton the lateral margin

Pleistocene gobiid fishes from Oita 113
preo
max
1mm
Fig. 1. Dorsal view of head region of a Pleistocene Rhinogobius giurinus, KMNH VP 100,117.
den, dentary; ecp, ectopterygoid; eth, ethmoid; exo, exoccipital; fro, frontal; max,
maxillary;ope, opercle;pal, palatine; prem, premaxillary; preo, preopercle; pto, pterotic;
qua, quadrate; supo, supraoccipital; sym, symplectic.
of the frontal and opens at the lateral end. The melanin of the eye ball is preserved in
KMNH VP 100,117 (Fig. 1). The dentary is narrow at the anterior part and deep at the
posterior part. Small unicuspid teeth are present on the premaxillary and the dentary
(Fig. 1). The ceratohyal is narrow at the anterior part and wide at the posterior part.
Four branchiostegals are attached on the ceratohyal. The epihyal is almost triangular in
shape. The posterior margin of the pectoral fin is circular. Other observable bones of
the head region are maxillary, quadrate, symplectic, palatine, ectopterygoid, opercle,
preopercle, supraoccipital, pterotic and exoccipital (Fig. 1). The first and second and the
third and fourth hypurals are fused. The parhypural is short. The haemal spine of the
second preuralcentrum is thick and wide. Other observable bones of the caudal region
are a part of the 5th hypural and a part of the epural (Fig. 2).

114 Yoshitaka Yabumoto
Fig. 2. Caudal region of a Pleistocene Rhinogobius giurinus, KMNH VP 100,122. epu, epural;
hes, haemal spine of the second preuralcentrum; hyu, hypural; parh, parhypural.
Rhinogobius brunneus (Temminck et Schlegel)
Material: KMNH VP 100,125, almost complete specimen with its left side exposed.
Standard length 26.0mm and number of vertebrae 10+16=26. This specimen is
identified by the form of the pelvic fin. KMNH VP 100,126, almost complete specimen
with its right side exposed. Standard length 24.3 mm and number ofvertebrae 10+16=
26. This specimen is identified by the form of the scales. KMNH VP 100,127, body
twisted at anal origin, all elements of skeleton, fin rays and scales are detached. This
specimen is identified by the form of the scales. KMNH VP 100,128, almost complete
specimen with its left side exposed, but ribs, pectoral, pelvic and anal fins missing.
Standard length 23.7 mm. This specimen is identified by the form of the scales.
KMNH VP 100,129, almost complete specimen with its left side exposed, but pelvic fins
missing. Standard length 35.8 mm and number of vertebrae 10+16=26. This speci
men is identified by the form of the scales. KMNH VP 100,130, specimen with its left

Pleistocene gobiid fishes from Oita 115
side exposed lacking first dorsal fin, caudal skeleton and caudal fin. This specimen is
identified by the form of the scales. KMNH VP 100,131, specimen with ventral side
exposed lacking caudal part. Some bones of head region preserved. This specimen is
identified by the form of the scales. Takayama's specimen 2, almost complete specimen
with its left side exposed, but first dorsal fin missing. Some bones of head region
disarticulated. Standard length 37.5 mm and number of vertebrae 10+16=26. This
specimen is identified by the form of the scales. KMNH VP 100,132, almost complete
specimen with its right side exposed, but a part of the anal fin missing. Standard length
37.4 mm and number of vertebrae 10+16=26. This specimen is identified by the form
of the scales. KMNH VP 100,133, almost complete specimen with its left side exposed,
and some bones of head region disarticulated. Standard length 27.0 mm and number of
vertebrae 10+16=26. This specimen is identified by the form of the scales. KMNH
VP 100,134, almost complete specimen with its left side exposed, but lacking some bones
of head region and a part of abdominal vertebrae. This specimen is identified by the
form of the scales. KMNH VP 100,135, caudal part of the body. This specimen is
identified by the form of the scales. KMNH VP 100,136, anterior part of the body.
This specimen is identified by the form of the scales. KMNH VP 100,137, caudal part of
the body, lacking upper part of the caudal skeleton.
This specimen is identified by the
form of the scales.
Distinguishing characters: The branching point of the innermost pelvic fin ray is
beside the branching point of the next ray. The posterior margin of each scale is round
in shape. The spines of each scale are almost equal in length and grooves extend two
pro
prem
den
max
Fig.3. Ventral view of head region of a Pleistocene Rhinogobius brunneus, KMNH VP
100,131. ang, angular; bra, branchiostegal; para, parashenoid; pro, prootic; other
abbreviations see Fig. 1.

116 Yoshitaka Yabumoto
thirds of the way from the anterior end.
Description: Scales are ctenoid. In the fossil specimens, the observable bones of
the head region are maxillary, premaxillary, dentary, angular, palatine, ectopterygoid,
quadrate, symplectic, frontal, parasphenoid, prootic, and branchiostegals. There are two
condyles on the anterior end of the maxillary. The middle part of the maxillary is broad.
Small unicuspid teeth are present on the premaxillary and the dentary. The palatine has
two processes and one acetabulum at the anterior end. The posterior margin connects
with the ectopterygoid which is pointed at the upper end. The lower end of the
ectopterygoid is wide and connects with the anterior margin of the quadrate which is
approximately triangular with a long process ventrally. The antero-ventral corner of the
quadrate is a condyle for the angular (Fig. 3). A pair of foramina is present at the middle
of the parasphenoid. The anterior quarter of the ventral surface of the parasphenoid is
slightly concave for the attachment to the prevomer. The prootichas a large foramen for
the facial nerve (Fig. 3). Forms of these observable bones are similar to those of Recent
R. brunneus.
Remarks: In the Recent species of the genus Rhinogobius, the first pair of normal
long ribs are attached to the third vertebra. The number of dorsal pterygiophores
correspond to the numberofdorsal fin rays. The space between the fifth and sixthspines
of the first dorsal fin is much wider than spaces between other spines of the fin. The
number of anal pterygiophores is one fewer than that ofanal fin rays. The haemalspine
of the first caudal vertebra is conspicuous (Fig.6). This information is useful in
determining the numbers of abdominal and caudal vertebrae, and the numbers of dorsal
and anal fin rays in Rhinogobius fossil material.
The following characters indicate that the fossil specimens are members of the
teleostean fish family Gobiidae of the order Perciformes: (1) the first and second dorsal
fins are present and are notcontinuous; (2) both pelvic fins are close together andsituated
below the pectoral fin; (3) the body is covered with ctenoid scale; (4) the hypural bones
arefused and simplified; (5) the dentary and premaxillary bear small conical teeth; (6) the
interorbital space is narrow. They have the following meristic characters: (1) the
number of abdominal vertebrae is 10 and the number of caudal vertebrae is 16; (2) the
first dorsal fin consists of6 spines and thesecond dorsal fin consists ofonespine and 8 soft
rays; (3) the anal fin also consists ofonespine and 8 soft rays. According to Masuda et
al. (1984), 35 species in 18 genera of gobiid fishes are found in freshwater in Japan.
Among them, the meristic characters of Rhinogobius giurinus and R. brunneus correspond to
that of the fossil specimens. Threespecies ofthe genus Rhinogobius have been reported in
Japan. The fossil specimens are not Rhinogobius flumineus, because R. fiumineus has 11
abdominal vertebrae. The differences between Recent R. giurinus and R. brunneus are
recognized in theforms ofthesucking disk ofthe pelvic fin andscales. Uyeno and Iwao
(1966) described the differences in the shape of the sucking disk and the number of
branches of the innermost pelvic fin ray. But these characters of the pelvic fin are not

Pleistocene gobiid fishes from Oita 117
1mm
CSs"^
1mm
Fig. 4. Pelvic fins of Recent and fossil specimens of the genus Rhinogobius. A, Recent R.
giurinus; B, Recent R. brunneus; C, fossil R. giurinus, KMNH VP 100,118; D, fossil R.
brunneus, KMNH VP 100,125. The lines indicate the branching points of fin rays.
1mm
Fig. 5. Scales of Recent and fossil specimens of the genus Rhinogobius. A and B, Recent R.
giurinus; C and D, Recent R. brunneus; E, fossil R. giurinus, KMNH VP 100,118; F,
fossil R. brunneus, KMNH VP 100,132.

Pleistocene gobiid fishes from Oita 119
observable in the fossil specimens from Kusu Basin, because the posterior part of the
pelvic fin is not preserved. In Recent R. giurinus and R. brunneus, there is a difference in
the position of the branching point of the innermost ray of the pelvic fin. The branching
point of the innermost ray is approximately in between the base and the branching point
of the next ray in R. giurinus (Fig. 4A). The branching point of the innermost ray is
beside to the branching point of the next ray in R. brunneus (Fig. 4B). This character is
observable in the fossil specimens (Fig. 4C and D).
In R.giurinus, the posterior end of the scale is slightly pointed and the spines are short
on the posterior corner and gradually become longer toward the dorsal and ventral ends of
the posteriormargin. Grooves extendclose to the posteriormargin of the scale (Fig.5B).
In R. brunneus, the posterior margin of the scale is round in shape and the spines are
almostequal in length. Grooves extend two thirdsof the way from the anterior end (Fig.
5C). In R. giurinus, scales similar to those of R. brunneus occur in a ratio of approximately
one to twenty (Fig. 5A). In R. brunneus, scales similar to those of R. giurinus occur in a
ratio of one to five or six (Fig. 5D). Two types of scales are recognized in the fossil
specimens (Fig. 5E and F). All of the observablescales in a fossil specimen are examined
for identification of species. Two species, R. giurinus and R. brunneus, are recognized
among fossil specimens on the bases of the characters of the pelvic fin and scales (Figs. 4C
and D, 5E and F).
Literature Cited
Iwauchi, A. and Y. Hase. 1987. Late Cenozoic vegetation and paleoenvironment of northern and
central Kyushu, Japan. Part 3. Southern part of Kusu Basin (Lower and Middle Pleistocene).
Jour. Geol. Soc. Japan, 93 (7): 469-489, figs. 1-13, tabs. 1-2, pis. 1-2.
Masuda, H., K. Amaoka, C. Araoa, T. Uyeno, and T. Yoshino (ed.). 1984. The fishes of the
Japanese Archipelago. Text. Tokai Univ. Press, xxii+437 pp., 245 figs.
Shuto, T. 1953. Younger Cenozoic history of Oita District, Kyushu (I). Jour. Geol. Soc. Japan, 59
(693): 225-240, figs. 1-8, tabs. 1-6.
Uyeno, T., S. Kimura, and Y. Hasegawa. 1975. Freshwater fishes from Late Cenozoic deposits in
Kusu Basin, Oita Prefecture, Japan. Mem. Natn. Sci. Mus. (8): 57-66, fig. 1, tabs. 1-2, pis. 6-9.
Uyeno, T. and Y. Iwao. 1975. Late Cenozoic gobiid fish from Togo Formation in Kagoshima
Prefecture, Japan. Bull. Natn. Sci. Mus., Ser. C (Geol.), 1 (2): 55-60, figs. 1-2, pis. 1-2.

Pleistocene Gobiid Fishes of the Genus Rhinogobius
from Kusu Basin, Oita Prefecture, Japan.
Yoshitaka Yabumoto
Plates 1-2

Explanation of Plate 1.
Photographs of the fossils of Rhinogobius giurinus (Rutter) from Kusu
Basin, Oita Prefecture.
A. lateral view of the left side (KMNH VP 100,118).
B. ventral view (KMNH VP 100,119).
C dorsal view (KMNH VP 100,117).
Scales indicate 10 mm.

Yabumoto, Y. Pleistocene gobiid fishes from Oita Plate 1
wtmm...
B
C

Plate2
I ;•••; !

Explanation of Plate 2.
Photographs of the fossils of Rhinogobius brunneus (Temminck et Schlegel)
from Kusu Basin, Oita Prefecture.
A. lateral view of the left side (KMNH VP 100,125).
B. lateral view of the left side (KMNH VP 100,129).
C lateral view of the right side (KMNH VP 100,132).
Scales indicate 10 mm.

Yabumoto, Y. Pleistocene gobiid fishes from Oita Plate 2
B
irp